Add New 2960x via Trunk port.

[M3KVII]

Hello,

    I need to add a new switch to an existing switch, and allow all the same vlans configured on it. I have a cable connected from gig1/0/4 on one switch going to gig2/0/1 on the new switch. I've completed the basic configuration from scratch and set up the ip addressing as seen below. 

ip address 192.168.254.10 255.255.255.240 

ip default-gateway 192.168.254.49

The trunk port on switch 1:

Name: Gi1/0/4
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 3 (USERS)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: 6 (VOIP)
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL

I configured the trunk port on switch to below: 

gig2/0/1 on the other switch. 

SW1#config t

SW1(config)#interface gig2/0/1
SW1(config-if)#switchport encapsulation negotiate
SW1(config-if)#switchport mode dynamic auto
SW1(config-if)#switchport trunk allowed vlan add 3
SW1(config-if)#end

Previously the switch shut down my connection and entered err-disable mode. I believe portfast is enabled and perhaps I had the wrong settings. Any help would be greatly appreciated, thank you in advance! 

[Francesco Molino]

Hi

Do you have access to switch 1? Can you share the config of your port g1/0/4?

It seems that your port on switch 1 is configured like :

interface g1/0/4

 switchport encapsulation negotiate

 switchport mode dynamic auto

 switchport access vlan 3

 switchport voice vlan 6

You need to have the same config on both side.

If you want to do it easly, do the config below:

On switch1:

default interface g1/0/4

interface g1/0/4

 switchport trunk encap dot1q

 switchport mode trunk

 switchport trunk allowed vlan x,x,x --> Only if you want to filter vlans that need to be trunked on the interface. Remove it if you want all vlans

On switch2:

default interface g2/0/1

interface g2/0/1

 switchport trunk encap dot1q

 switchport mode trunk

 switchport trunk allowed vlan x,x,x --> Only if you want to filter vlans that need to be trunked on the interface. Remove it if you want all vlans

[M3KVII]

Thank you for your response. I had a similar situation with a different switch I provisioned and your explanation worked that time exactly as you described. However I fear in this case something continues to shut down my switch and leaves it in err-disable once I connected it. 

THis is the out put of Switch1 That I am using to configure the trunk between both switches. The other one is essentially a blank slate as far as the trunk port and basic security configuration on the switch. Thanks again for your response. !! 

Switchname#show interface gig1/0/4
GigabitEthernet1/0/4 is down, line protocol is down (notconnect)
Hardware is Gigabit Ethernet, address is 042a.e2f7.9d04 (bia 042a.e2f7.9d04)
Description: s@dm1n
MTU 1500 bytes, BW 10000 Kbit/sec, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Auto-duplex, Auto-speed, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 6w2d, output 6w2d, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
13531 packets input, 3098264 bytes, 0 no buffer
Received 1322 broadcasts (829 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 829 multicast, 0 pause input
0 input packets with dribble condition detected
242486 packets output, 33693834 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

[Francesco Molino]

You changed the config and said that it worked right?
However you still have err-disable state?

Can you share the config of both switches and logs to see what causing this err-disable?

[amikat]

Hi,

Please be aware that leaving both interfaces in the default switching mode (ie. dynamic auto) does NOT give you a trunk link. The interface with dynamic auto mode converts the link to a trunk link only if the neighbouring interface is set to trunk or desirable mode.

Best regards,

Antonin

[M3KVII]

I understand I must set both to:

#switchport interface trunk

In order for the configuration to take on both sides. 

[amikat]

Hi,

configuring "switchport mode trunk" at both sides is certainly an option. You can also leave one side at the default (ie. dynamic auto) and configure the other side as "switchport mode trunk" or "switchport mode dynamic desirable". There are other options available.

Best regards,

Antonin